Avance 400 nmr spectrometer

¹H, ¹³C and 2D-NMR spectra were measured on an Avance 400 NMR spectrometer (¹H-NMR: 400 MHz and ¹³C-NMR: 100 MHz, Bruker, Uster, Switzerland). Silica gel column chromatography (SCC) was performed on silica gel 60 (Sigma-Aldrich, Darmstadt Germany; 230–400 mesh). Reversed phase column chromatography (RPCC) was performed on C18-reversed phase silica gel for column chromatography (Sigma-Aldrich, Darmstadt, Germany). Diaion HP-20 stationary phase (Sigma-Aldrich, Darmstadt, Germany). Pre-coated silica gel 60 F254 plates (0.25 mm and 1000 μm in thickness, Sigma-Aldrich, Darmstadt, Germany) were used for thin layer chromatography (TLC), with 10% vanillin in ethanol spray reagent as a visualizing agent with a hotplate (150 °C). High-performance liquid chromatography (HPLC) apparatus (Agilent, 1200 series, Waldbronn, Germany) equipped with a degasser, autosampler, quaternary pump and PDA detector and Discovery^® C18 (5 cm × 4.6 mm × 5 μm) column (Supelco, Bellefonte, Pennsylvania, USA) were used. An isocratic mode elution equipped with an acetonitrile:water blend (75:25 v/v) with a flow rate of 1 mL/min was used. The injection volume was 10 μL (from 60 mg/mL, sample in methanol). The chromatogram was monitored using Agilent Chemstation software (Version B.2.4.1). Analytical grade chemicals and reagents were used.

All the chemicals used for the synthesis were procured from Merck (Mumbai, India), Sigma (Mumbai, India), HiMedia (Mumbai, India) or Qualigens (Mumbai, India) and used without further purification. The progress of each reaction was monitored by ascending thin layer chromatography (TLC) using pre-coated silica gel F254 Alumina TLC Plates (Merck) and the spots were visualized with UV light and iodine vapor. Elemental analyses (C, H, and N) were done with a Flashea 112 analyzer (Shimadzu, Mumbai, India) and all analyses were consistent (within 0.4%) with theoretical values. IR spectra were recorded on a PS 4000 FTIR instrument (Jasco, Tokyo, Japan) using KBr pellets. ¹H-(400 MHz) and ¹³C-NMR (100 MHz) spectra were recorded in DMSO-d₆ on an Avance 400 NMR spectrometer (Bruker, Billerica, MA, USA) fitted with an Aspect 3000 computer and all the chemical shifts (δ ppm) were referred to internal TMS for ¹H and the solvent signal for ¹³C-NMR. ¹H-NMR data are reported in the order of chemical shift, multiplicity (s, singlet; d, doublet; t, triplet; q, quartet; br, broad; br s, broad singlet; m, multiplet and/or multiple resonance), number of protons. A Micro TOF-Q-II (Bruker Daltonics, Billerica, MA, USA) with electron spray ionization (ESI) was used to obtain the HRMS data.

Solvents and organic reagents were purchased from Sigma Aldrich and Merck (Germany) and were used without further purification. Elemental analyses were performed on HeraeusVario EL III analyzer. The results were within ± 0.4% of the theoretical values. FT-IR spectra were recorded using a Thermo Nicolet 380 instrument equipped with a Smart Orbit ATR attachment. ¹H and ¹³C NMR spectra were recorded at ambient temperature on a Bruker AVANCE 400 NMR spectrometer using standard parameters. All chemical shifts are reported in δ units with reference to the residual peaks of CDCl₃ (δ 7.24, ¹H NMR; δ 77.0, ¹³C NMR) or DMSO-d₆ (δ 2.50, ¹H NMR; δ 39.52, ¹³C NMR). ESI-MS was recorded on a MICROMASS QUATTRO II triple quadrupole mass spectrometer. Precoated aluminum sheets (silica gel 60 F₂₅₄, Merck Germany) were used for thin-layer chromatography (TLC) and spots were visualized under UV light.

Epoxidized natural rubber with about 50% epoxy content (designated as ENR50) and with relative Mw of 3.8 × 10⁵ g/mol was supplied by the Malaysian Rubber Board, Kuala Lumpur, Malaysia. The actual epoxy content was determined using Bruker Avance-400 NMR spectrometer and was found to be 51.05%. The spent coffee ground was obtained from Starbucks, Gelugor Penang. The other compounding ingredients, such as sulphur, zinc oxide, Stearic acid, sulfenamide (CBS), and carbon black N330, were purchased from Bayer Ltd. (Penang, Malaysia) and used as received.